The major objective of the proposed research is to determine the concurrent and residual effects of low level lead exposure on the fetal and infant rhesus monkey. In the current grant year, a new infant monkeys have been obtained from mothers carrying blood lead (PbB) burdens in the approximate range of 35-70 ug/dl. Some of these infants are being nursed by mothers maintained on their leaded diets and others are being reared with comparable amounts of lead added to their nursery milk until the end of the first year of life. Behavioral tests to assess social behavior and locomotor activity have been intiated with these animals and will continue throughout the current grant year. In addition, monkeys exposed either in utero or post-natally to similar schedules of Pb burdens in previous years, will be tested on various tasks to assess the persistence of earlier seen behavioral effects of lead or to determine if delayed or more exaggerated symptoms appear with neurobehavioral development. These behavioral measures are supported with data on general health, body weight, food intake, PbB levels, and other clinical observations.